Modulated physiological sensor

ABSTRACT

A modulated physiological sensor is a noninvasive device responsive to a physiological reaction of a living being to an internal or external perturbation that propagates to a skin surface area. The modulated physiological sensor has a detector configured to generate a signal responsive to the physiological reaction. A modulator varies the coupling of the detector to the skin so as to at least intermittently maximize the detector signal. A monitor controls the modulator and receives an effectively amplified detector signal, which is processed to calculate a physiological parameter indicative of the physiological reaction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/584,447, filed Aug. 13, 2012, which claims priority benefitunder 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No.61/524,744, filed Aug. 17, 2011, titled Modulating Physiological Sensorand U.S. Provisional Patent Application Ser. No. 61/639,985, filed Apr.29, 2012, titled Modulated Physiological Sensor, both provisionalapplications hereby incorporated in their entirety by reference herein.

BACKGROUND OF THE INVENTION

From a physiological perspective, the human body comprises a set ofinteracting systems, each having specific functions and purposes. Thesesystems maintain the body's internal stability by coordinating theresponse of its parts to any situation or stimulus that would tend todisturb its normal condition or function. The nervous system includesthe central nervous system and the peripheral nervous system. Thecentral nervous system is the brain and the spinal cord. Themusculoskeletal system includes the skeleton and attached muscles andincludes bones, ligaments, tendons, and cartilage. The circulatorysystem includes the heart and blood vessels, including arteries, veinsand capillaries. The respiratory system includes the nose, trachea andlungs. The gastrointestinal system includes the mouth, esophagus,stomach, intestines, liver, pancreas and gallbladder. The integumentarysystem includes the skin, hair, nails, sweat glands and sebaceousglands. The urinary system includes the kidneys and bladder. The immunesystem includes white blood cells, thymus and lymph nodes. The endocrinesystem includes the pituitary, thyroid, adrenal and parathyroid glands.

Various sensors may be applied for analyzing and measuring the processesoccurring in the above-cited physiological systems and for generatingphysiological parameters indicative of health or wellness as a result.As one example, a pulse oximetry sensor generates a blood-volumeplethysmograph waveform from which oxygen saturation of arterial bloodand pulse rate may be determined, among other parameters. As anotherexample, an acoustic sensor may be used to detect airflow sounds in thelungs, bronchia or trachea, which are indicative of respiration rate.

SUMMARY OF THE INVENTION

The physiological systems cited above maintain the stability, balanceand equilibrium of a living being. Modulation may be advantageously usedto accentuate detection of processes occurring within thesephysiological systems. An example of natural modulation is tissuevibration in the trachea due to the inflow and outflow of air betweenthe lungs and the nose and mouth. This vibration creates sound waves ata higher frequency than the underlying respiration. An acoustic sensorutilizing a piezoelectric device attached to the neck is capable ofdetecting these sound waves and outputting a modulated sound waveenvelope that can be demodulated so as to derive respiration rate. Anacoustic respiration rate sensor and corresponding sensor processor isdescribed in U.S. patent application Ser. No. 12/904,789, filed Oct. 14,2010, titled Acoustic Respiratory Monitoring Systems and Methods,assigned to Masimo Corporation, Irvine, Calif. (“Masimo”) andincorporated by reference herein.

Another example of natural modulation is pulsatile arterial blood flowat a peripheral tissue site, such as a fingertip, resulting frompressure waves generated by the heart. An optical sensor generates aplethysmograph waveform responding to changes in a light absorption dueto the pulsatile blood flow so as to measure blood composition, such ashemoglobin constituents. This plethysmograph also modulates arespiration envelope that can be demodulated so as to derive respirationrate.

An example of artificial modulation is a physiological sensor having anaccelerometer and a vibration element mounted on a substrate so that thevibration element is in mechanical communications with theaccelerometer. An interface communicates at least one axis of theaccelerometer signal to a monitor. The substrate is attached to the skinsurface of a living being, and the vibration element is activated so asto modulate the skin surface coupling at a modulation frequency. In anembodiment, an artificially-modulated sensor is responsive torespiratory-induced movements at the skin surface.

One aspect of a modulated physiological sensor is a noninvasive sensorresponsive to a physiological reaction of a living being to an internalor external perturbation that propagates to a surface area of the livingbeing. The modulated physiological sensor has a detector configured tocommunicate with a surface area of a living being so as to generate asignal responsive to a physiological reaction of the living being to theperturbation. A modulator varies the coupling of the detector to thesurface area so as to at least intermittently maximize the detectorsignal. A monitor controls the modulator and receives a detector signalso as to calculate a physiological parameter indicative of aphysiological state of the living being.

In various embodiments, the modulator is a vibration element thatmechanically accentuates the coupling of the detector to the surfacearea. A substrate co-mounts the detector and the vibration element. Anattachment releasably affixes the substrate, detector and vibrationelement to the surface area. In an embodiment, the detector is anaccelerometer and the vibration element is a coin motor. The substrateis a circuit board that mechanically mounts and electricallyinterconnects the accelerometer and coin motor. The attachment is a tapehaving a sticky side that attaches to the surface area and a housingside that encloses the circuit board.

Another aspect of a modulated physiological sensor is a sensing methodthe provides a detector responsive to a physiological wave generatedwithin a living being that propagates to a skin surface and couples thedetector to the skin surface. The detector coupling is modulated so asto generate a modulated detector output indicative of the physiologicalwave. The detector signal is demodulated so as to derive a physiologicalsignal, and a physiological parameter is determined from thephysiological signal. In various embodiments, the modulation isvibration of the detector by co-mounting the detector and a vibrationelement. The detector and the vibration element may be co-mounted to acommon substrate, which is attached to the skin surface. A seconddetector and a second vibration element may be mounted to the commonsubstrate and isolated from the combination detector and vibrationelement.

A further aspect of a modulated physiological sensor is a detector meansfor responding to physiological propagations reaching a skin surface ofa living being and a modulator means for varying the coupling of thedetector means to the skin surface. A monitor demodulates a sensorsignal from the detector means so as to analyze the physiologicalpropagations and generate a physiological parameter output. In variousembodiments, a substrate means mounts the detector means and themodulator means and an attachment means secures the substrate to theskin surface. A control signal from the monitor sets a frequency of themodulator means above a low frequency cutoff of the detector means. Inan embodiment, the modulator means is a vibration element, the detectormeans is multiple detectors, the modulator means is multiple vibrationelements and the substrate means incorporates at least one isolationelement so as to isolate detector and vibration element pairs. In anembodiment, the vibration element remotely modulates the detector via anacoustic wave.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general block diagram of a modulated physiological sensor incommunications with the physiological systems of a living being;

FIG. 2 is general block diagram of a modulated physiological sensorembodiment;

FIGS. 3A-D are amplitude vs. time and corresponding amplitude vs.frequency graphs of a physiological reaction and a correspondingmodulated and detected reaction;

FIG. 4 is a general block diagram of a vibration-modulated physiologicalsensor embodiment;

FIG. 5 is a general block diagram of a multi-element,vibration-modulated sensor embodiment;

FIGS. 6A-F are side views of various modulated physiological sensorembodiments;

FIG. 7 is a general block diagram of a vibration-accelerometerphysiological sensor embodiment;

FIG. 8 is a detailed block diagram of a vibration-accelerometerphysiological sensor embodiment;

FIG. 9A-B are assembled and exploded perspective views, respectively, ofa vibration-accelerometer physiological sensor embodiment; and

FIG. 10 is a graph of a vibration-accelerometer physiological sensoroutput versus time illustrating three-axis of respiration envelopes withthe vibration turned on and off.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 generally illustrates a modulated physiological sensor 100 incommunications with the physiological systems 20 of a living being 10.Physiological reactions 50 to external 30 or internal 40 perturbationspropagate to the body surface 12 and are coupled 110 to one or moredetectors 120. These physiological reactions 50 are indicative of statesand processes of the physiological systems 20. The detectors 120 areresponsive to coupled physiological reactions 112 so as to generatedetector outputs 122. One or more monitors 20 are responsive to thedetector outputs 122 so as to compute physiological parameters 6 thatquantify the states and processes of the physiological systems 20. Thecoupling(s) 110 is advantageously modulated 130 under control of themonitor(s) 20 so as to accentuate detection of the physiologicalreactions 50, as described in further detail below.

As shown in FIG. 1, detectors 120 include any device that is responsiveto the coupled physiological reactions 112 such as optical, acoustical,electrical, mechanical, chemical and thermal mechanisms, to name a few.The detector outputs 122 may include blood photo-plethysmographs, ECG,EEG and body sound waveforms; indications of skin color, temperature,movement or pressure; and chemical responses and measurements ofmoisture, breath, sweat or odors, to name a few. The monitor(s) 20 mayinclude any or all devices or combinations of devices that areresponsive to the detector outputs 122 alone or in combination so as tocalculate or otherwise derive physiological parameters 6 that measure,graph, quantify or otherwise indicate one or more aspects of thephysiological systems 20 and corresponding states and processescorresponding to the physiological reactions 50. Parameter examplesinclude circulatory system measurements such as oxygen saturation, heartrate, blood glucose and blood pressure; and respiratory systemmeasurements such as respiration rate and volume, to name but a few.Parameters 6 can also include indications of specific abnormalphysiological conditions such as sleep apnea, anemia and hypoglycemia,to name a few.

Also shown in FIG. 1, external perturbations 30 may be natural, such aschanges to a person's physical environment including temperature,pressure, light and sound, for example. External perturbations 30 alsomay be artificial, such as the mechanical pressure induced by arespirator for breathing assistance or by a pulser on a fingertip formeasuring venous oxygen saturation as examples. Internal perturbations40 include normal and abnormal functioning and interactions of variousphysiological systems 20, including circulatory and respiratoryfunctions, to name a few. Internal perturbations 40 may also beartificial, such as due to a pacemaker or other implanted device.Physiological reactions 50 resulting from external perturbations 30 orinternal perturbations 40 include, as examples, a body surface expansionor contraction due to, say, lung inflation/deflation; an acoustic wavearriving from within the body to the body surface due to a heart beat orbowel sound; or a transverse wave traveling along the body surface dueto a muscle spasm. In general a physiological reaction 50 may be anoptical, acoustical, electrical, mechanical, chemical or thermalimpulse, wave or other variation or change. Further, externalperturbations 30 or internal perturbations 40 need not be the same typeor kind (e.g. optical, acoustical, electrical, mechanical, chemical orthermal) as the corresponding physiological reaction 50 or the detectorelement 120 responsive to the physiological reaction 50. For example, aninjection (external chemical perturbation) may trigger a heartarrhythmia that results in an acoustic and a mechanical wave(physiological reaction) that propagates to the skin surface and isdetected by an acoustical or mechanical sensor, or both. Further, theheart arrhythmia may result in an arterial pulse abnormality thatchanges the optical characteristics of a tissue site as measured by anoptical sensor attached to the tissue site.

FIG. 2 illustrates a modulated physiological sensor 200 embodiment thatattaches to a body surface 12 and is configured to respond tophysiological reactions 50, as described above. The sensor 200 has acoupling 210, a detector 220, an interface 230 and a modulator 240. Amonitor (not shown) outputs controls 232, 234 to the sensor 200 andreceives signals 232 from the sensor 200. The interface 230 communicatesdetector signals 222 to the monitor in response to drive controls 222 tothe detector 220. The interface 230 also communicates a modulatorcontrol 242 to the modulator 240. The modulator 240 responds to themodulator control 242 so as to generate a modulation 244 to the coupling210.

As shown in FIG. 2, the modulator 240 varies the coupling 210 of thedetector 220 to the body surface 12 and hence to the physiologicalreaction 50. In particular, the body surface 12 of a person, includingskin and underlying tissues, varies by individual and, indeed, bylocation on a particular individual. These variations are in shape,texture, color and elasticity to name a few. As such, a fixed couplingis unlikely to provide an optimum body surface/detector interface.Indeed efficient and effective body surface/detector coupling is anissue for most if not all physiological sensors. For example, common ECGelectrodes require a conductive gel so as to effectively couple to askin surface. The modulator 240 advantageously continuously varies thedetector coupling 210 to the skin surface across a range of contactforces at the skin/sensor interface. For an electrical detector, say,this varied coupling alters the detector electrical resistance at theskin surface over a range of values. For a mechanical detector, thevaried coupling alters the mechanical impedance of the detector at theskin surface over a range of values. For an acoustic detector, forexample, the varied coupling alters the acoustical impedance of thedetector at the skin surface over a range of values. As a result of thisvariable detector coupling to the skin surface, the detector has maximaland minimal coupling each modulation cycle. Further, the modulationfrequency may be set above any detector low frequency response cutoffs.Accordingly, the modulation advantageously amplifies the detector signal222, as described in further detail with respect to FIGS. 3A-D, below.

FIGS. 3A-D illustrate a physiological system reaction to perturbationsand a corresponding modulated and detected sensing of the reaction. FIG.3A is an exemplar time domain graph 310 of a relatively low amplitude,low frequency physiological system reaction 301 to some form of internalor external perturbation. FIG. 3B is a corresponding exemplar frequencydomain graph 320 of the physiological system reaction 301. Thephysiological reaction 301 may be difficult to detect due to either asmall amplitude signal 301 or a signal frequency f_(r) 302 less than thedetector cutoff frequency f_(c) 304, i.e. outside the detector passband303.

FIG. 3C is an exemplar time domain graph 330 of a modulated detectorresponse 305 to the reaction 301 (FIG. 3A) described above. The response305 has a modulation 306 and an envelope 307. In particular, thephysiological sensor 200 (FIG. 2) has a modulated coupling 210 (FIG. 2)that achieves or approaches a maximal coupling of a detector 220 (FIG.2) to a body surface 12 (FIG. 2) at least once per modulation cycle, asdescribed with respect to FIG. 2 above. Accordingly, the modulateddetector 220 (FIG. 2) accentuates the physiological signal 301 (FIG. 3A)during the maximal coupling and de-accentuates the physiological signal301 (FIG. 3A) during the minimal coupling. This cyclicalaccentuation/de-accentuation generates an envelop 307 that is,effectively, an amplification of the physiological reaction 301 (FIG.3A).

FIG. 3D is an exemplar frequency domain graph 340 of a modulatedphysiological sensor response 305 (FIG. 3C). In various embodiments, themodulation frequency f_(mod) 308 is set substantially higher than anylow frequency cutoff f_(c) 304 of the detector so that the sensorresponse 305 is well within the detector passband 303 (FIG. 3B).

As described with respect to FIGS. 3A-D, in various embodiments anamplified version of the physiological response 301 (FIG. 3A) is derivedfrom the sensor response 305 (FIG. 3C) by any of various well-known AMdemodulation techniques. These include envelope detection with arectifier or product detection utilizing multiplication by a localoscillator, to name a few.

FIG. 4 illustrates a vibration-modulated physiological sensor 400embodiment. The sensor 400 has a detector 410, a vibration element(“vib”) 420, a substrate 430 and an interface 440 to a monitor. Thedetector 410 and the vib 420 are both mounted to the substrate 430. Inan embodiment, the detector 410 is mounted so as to directly couple 401to the body surface 12. For example, the detector 410 may be mountedthrough the substrate 430, as shown. In other embodiments, the detector410 is attached adjacent the substrate 430. In additional embodiments,the detector 410 may not contact the body surface 12 at all, such aswith an accelerometer-based detector described with respect to FIGS.7-10, below. In an embodiment, the vib 420 is a coin motor, as describedwith respect to FIGS. 7-10, below. In other embodiments, the vib 420 isany of various off-balance motors, voice coils or similarelectro-mechanical devices. In further embodiments, the vib 420 is anymechanical, electromagnetic, piezoelectric, pneumatic, electric,acoustic or magnetic device that vibrates in response to an electricalsignal.

As shown in FIG. 4, the detector 410, and hence the coupling 401, isvibration-modulated 420 via the substrate 430. The substrate 430 may beany material that effectively transmits or conducts vibrations from thevib 420 to the detector 401. In an advantageous embodiment, thesubstrate 430 is a circuit board material that provides mechanicalmounts for and supports electrical interconnects between the sensorcomponents.

Also shown in FIG. 4, a monitor (not shown) outputs controls 442, 444 tothe sensor 400 and receives signals 442 from the sensor 400. Theinterface 440 communicates detector signals 412 to the monitor inresponse to drive controls 412 to the detector 410. The interface 440also communicates a vibration control 422 to the vib 420. The vib 420responds to the vibration control 422 so as to generate a modulation tothe coupling 401 via the substrate 430. In various embodiments, thedetector 410 may be mechanical, such as an accelerometer described withrespect to FIGS. 7-10, below. In other embodiments, the detector 410 maybe electrical, such as an electrode for sensing ECG or EEG signals; oroptical such as a photodiode; or acoustical, such as a piezoelectricdevice; or thermal, such as a thermopile, pyrometer, thermistor,thermocouple, IR photodiode or temperature diode, to name a few.

FIG. 5 illustrates a multiple-element, vibration-modulated sensor 500embodiment having a two or more sensor elements 510, 520, one or morevibration elements (vibs) 530, 540, a substrate 550 and an interface 560to a monitor. The sensor elements 510, 520 may each be detectors or acombination of one or more detectors and one or more emitters. In anembodiment, the sensor elements 510, 520 are different types ofdetectors. For example, element1 510 may be mechanical and element2 maybe electrical. In an embodiment, the sensor elements 510, 520 may be anemitter and a corresponding detector. For example, element1 510 may bean LED for illuminating a tissue site and element2 520 may be a opticaldetector, such as a diode or diode array, for receiving the LEDillumination after attenuation by the tissue site. Advantageously,multiple elements 510, 520 on a single substrate 550 provide an array oflike sensors for increased detection capability or for directionalsensing capability, such as determining the source of a body sound asbut one example. Advantageously, multiple elements 510, 520 on a singlesubstrate 550 provide an array of different sensors in a single sensorpackage for simultaneous detection and analyses of multiple types orkinds of physiological responses to the same or different external orinternal perturbations.

As shown in FIG. 5, multiple vibs 530, 540 may be separated by asubstrate isolator 570. In this manner, vib1 530 solely effects thecoupling 501 of element1 510 to a body surface 12 and, likewise, vib2540 solely effects the coupling 502 of element2 520 to a body surface12. Multiple isolated vibs 530, 540 advantageously allow each vib 530,540 output to be adapted or otherwise suited to a particular element510, 520, both in terms of amplitude and frequency. In an embodiment,the isolator 570 is a material that significantly attenuatesmechanical/acoustical waves at the vib frequency or frequencies.

Also shown in FIG. 5, a monitor (not shown) outputs controls 562 to thesensor 500 and receives signals 562 from the sensor 500. The interface560 communicates element signals 512, 522 to the monitor in response todrive controls 512, 522 to the elements 510, 520. The interface 560 alsocommunicates vibration (vib) controls 564 to the vibs 530, 540. The vibs530, 540 respond to the vib controls 564 so as to generate a modulationto their respect couplings 501, 502.

FIGS. 6A-F illustrate various modulated physiological sensorconfigurations. As shown in FIG. 6A, an integrated sensor embodiment 610has a substrate 612, a detector 614, a vibration element (vib) 615, I/O(input/output) 617, an attachment 618 and electrical communication 619to a monitor or similar device (not shown). The substrate 612 mounts thedetector 614, vib 615 and I/O 617. In an embodiment, the substrate 612also provides electrical trace interconnects between the I/O and boththe detector 614 and vib 615. The I/O 617 transmits/receives sensorsignals/controls and, in particular, drive to the vib 615 and signalsfrom the detector 614. The attachment 618 adheres the substrate 612 andmounted components 614-617 to a body surface. In an embodiment, thedetector 614 is mounted through the substrate 612 so as to coupledirectly to a body surface or via the attachment 618. The vib 615advantageously modulates the coupling of the detector 614 to the bodysurface via the substrate 612 on which the detector 614 and vib 615 areco-mounted.

As shown in FIG. 6B, a semi-integrated sensor embodiment 620 has asubstrate 622, a detector 624, a vib 625, I/O 627, an attachment 628 andelectrical communication 629 to/from a monitor or other control ordisplay device. The semi-integrated sensor embodiment 620 is similar tothe integrated sensor embodiment 610 except that the I/O 627 is externalto the sensor 620 and may be mounted in the monitor (not shown) or in apod (not shown) between the sensor 620 and monitor. The I/O 627 is inelectrical communications 626 with the detector 624 and vib 625, such asvia cabling or other interconnect technology. The I/O 627 is also inelectrical communications 629 with a monitor.

As shown in FIG. 6C, a substrate-less sensor embodiment 630 has adetector 634, a vib 635, I/O 637, an attachment 638 and electricalcommunications 639, which transmits signals and controls between the I/O637 and a monitor or similar device (not shown). In this embodiment, thedetector 634 or more specifically the detector package, such as a chipcarrier, substitutes for a substrate. Accordingly, the vib 635 and I/O637 are mounted within or on or otherwise directly coupled to thedetector 634 package so that the detector 634 package is directlycoupled to the body surface and held in place with the attachment 638.In an embodiment, the attachment 638 is simply an adhesive layer on thedetector 634 package.

As shown in FIG. 6D, a sensor array embodiment 640 has a substrate 642,multiple detectors 644, a vib 645, I/O 647, an attachment 648 andelectrical communication 649. The sensor array embodiment 640 is similarto the semi-integrated embodiment 620 (FIG. 6B) except for the multipledetectors 644. The detectors 644 may be all the same device type(mechanical, electrical, acoustical, etc.), all different or a mixtureof one or more sub-arrays of the same device type with one or moredifferent device types. Advantageously, multiple detectors 644 on asingle substrate 642 provide an array of like sensors for increaseddetection capability or for directional sensing capability, such asdetermining the source of a body sound. Advantageously, multipledetectors 644 on a single substrate 642 provide an array of differentdetectors in a single sensor package for simultaneous detection andanalyses of multiple types or kinds of physiological responses to thesame or different external or internal perturbations. Advantageously, amix of detectors and transmitters (not shown), such as one or more LEDsand one or more photodiode detectors, provide active sensingcapabilities, such as illuminating and analyzing arterial (pulsatile)blood flow. Advantageously, one or more vibs 645 may provide bothmodulation and an active pulse for, say, analyzing non-pulsatile(venous) blood flow, as but one example.

As shown in FIG. 6E, a non-integrated sensor embodiment 650 has adetector 654, a vib 655 and attachments 658. The detector 654 and vib655 are separately attached 658 to a body surface. The I/O 657 is inelectrical communications 656 with the detector 654 and vib 655, such asvia cabling or other interconnect technology, including wireless.Further, the I/O 657 is external to the sensor 650 and may be mounted inthe monitor (not shown) or in a pod (not shown) between the sensor 650and monitor with electrical communications 659 between the I/O 657 andthe monitor. Advantageously, the vib 655 is attached to the body surfacein close proximity to the detector 654 so that surface waves 601generated by the vib in the body modulate the coupling between thedetector 654 and the body surface.

As shown in FIG. 6F, a remote sensor embodiment 660 has a detector 664and a modulation module 665. The modulation module 668 has a vib 665 andI/O 667. Advantageously, the vib 665 remotely modulates the detector 664when brought into proximity to the detector 664. In particular, the vib665 generates an acoustic wave 602 that vibrates the detector so as tomodulate the detector coupling to the body surface. In particular, theacoustic wave 602 propagates through media intervening between the vib665 and the detector 664. That media may be an air gap when the module668 is positioned immediately over the detector 664 or the media may betissue when the module 668 is positioned immediately over or on the bodysurface proximate the detector 664.

FIG. 7 generally illustrates a modulated physiological sensor 700embodiment having an accelerometer 710 and a vibation element (vib) 720mounted on a common substrate 730. An attachment (not shown) adheres orotherwise couples the substrate 730 to a body surface 12. Theaccelerometer 710 has three outputs 712 responsive to accelerations inthree dimensions (x, y, z) advantageously enabling the sensor 700 todetect both the amplitude, direction and/or type of propagations(translational 85, 87 and longitudinal 86, 88) and whether thepropagations are body waves 85, 86 or surface waves 87. The vib 720mechanically modulates the coupling of the substrate 730 and,accordingly, the coupling of the accelerometer 710 to the body surface12. The vib 720 frequency is selected to be substantially higher thanthe frequency of the propagations 85-88. As such, the accelerometer x, yand z outputs 712 are each amplitude modulated (AM) representations ofthe propagations 85-87. Advantageously, the modulated couplingsubstantially amplifies the propagations due to a peak AC couplingoccurring once every cycle of the vib. That peak AC coupling issubstantially greater than can be practically achieved with any staticcoupling of the accelerometer to the body surface 12. Accordingly, verylow amplitude propagations can be detected and measured to yieldphysiological parameters. See, for example, a respiration rate sensordescribed with respect to FIGS. 8-10, below.

FIG. 8 is a detailed block diagram of a vibration-modulatedphysiological sensor 800 embodiment. The sensor 800 has an attachment810, a substrate 820, an accelerometer 830, a coin motor 840 thatgenerates vibration modulation, an accelerometer interface 850, a speedcontrol 860 and monitor inputs/outputs (I/O) 801, 802. In an embodiment,the accelerometer 830 is an LIS352AX±2g full scale, analog output,3-axis (X, Y and Z) linear accelerometer available fromSTMicroelectronics, Geneva, Switzerland. In an embodiment, the coinmotor 840 is a 10 mm coin motor 310-101 available from PrecisionMicrodrives Ltd., London, UK. In an embodiment, the substrate 820 is acircuit board material that mechanically mounts and electricallyinterconnects the accelerometer 830, the coin motor 840, theaccelerometer interface 850 and the speed control 860. In an embodiment,the attachment 810 is a sticky tape that mounts the sensor 800 to a bodysurface of a living being. In an embodiment, the monitor I/O 802 to thespeed control is via a I²C bus. In an embodiment, the monitor I/O 801 tothe accelerometer 830 includes a multiplexer control input to theaccelerometer 830 to select one of the X, Y and Z axis for theaccelerometer output 832 to the monitor. In another embodiment, all ofX, Y and Z axes are simultaneously provided on the accelerometer output832.

FIGS. 9A-B are assembled and exploded illustrations, respectively, of avibration-modulated (vib) physiological sensor embodiment 900 that canbe attached to a skin surface proximate various parts of a person'sbody, such as the chest, ribs, stomach, waist, arms or back so as to,for example, determine respiration-related parameters. In anotherembodiment, a modulated physiological sensor 900 may have an opticalsensor (emitter and detector) combined with the accelerometer and vib.In this manner, the sensor can generate physiological measurements ofpulsatile blood flow for blood constituent analysis, physiologicalmeasurements of non-pulsatile (venous) blood flow artificially pulsed bythe vib and respiration measurements based upon either or both ofpleth-modulated optical sensor waveforms and vib-modulated mechanical(accelerometer) waveforms.

FIG. 10 is a vibration-accelerometer physiological sensor output 1000illustrating three-axis respiration envelope amplitudes 1010 versus time1020. The vibration continuously modifies the coupling of theaccelerometer to the skin, which effectively multiples the measuredacceleration due to respiration by that due to the vibration. Thisyields AM modulation waveforms 1001-1003 that display a (greatlymagnified) respiration envelope. This effect is amply illustrated incomparing the difference in the accelerator response when the vibration(coupling modulator) is turned on 1012 and off 1014.

There are various applications for a modulated physiological sensor, asdescribed above. A chest mounted sensor could monitor for sleep apnea athome, as well as in the hospital for patients receiving narcotics in thegeneral wards. An abdomen-mounted sensor could monitor bowel sounds togive a quantifiable measurement to peristalsis. A dual sensorconfiguration, with one sensor mounted on the upper part of the abdomenand one on the lower part, is used for diagnosing bowel obstruction,small bowel volvulus or intussuception. A sensor mounted over the radialartery would yield a semi-continuous blood pressure measurement. Anotherconfiguration is a screening tool for sub-clinical stenosis of majorvessels. For example, rather than placing a stethoscope over the carotidarteries or the abdomen to listen to flow through the aorta, a modulatedsensor could give a more quantifiable measurement of stenosis, one levelbetter than auscultation but one level below imaging. Anotherapplication is the differential diagnosis of heart murmurs aided bynoise cancellation of breathing and other mechanical movements so as todistinguish distinctive murmur patterns (e.g. crescendo/decrescendo).

A modulated physiological sensor has been disclosed in detail inconnection with various embodiments. These embodiments are disclosed byway of examples only and are not to limit the scope of the claims thatfollow. One of ordinary skill in art will appreciate many variations andmodifications.

What is claimed is:
 1. A physiological monitoring system comprising: amodulated physiological sensor comprising: a vibrational elementconfigured to generate vibrations; an accelerometer coupled with asurface area of a skin of a patient, said accelerometer configured todetect a physiological signal responsive to a respiration process; anoptical sensor configured to detect a plethysmographic waveform, whereinthe physiological signal and the plethysmographic waveform are modulatedby the vibrations; and one or more hardware processors configured todetect respiration parameter based on the modulated physiological signaland the modulated plethysmographic waveform.
 2. The physiologicalmonitoring system of claim 1, wherein the modulated physiological sensoris configured to be placed proximate a radial artery.
 3. Thephysiological monitoring system of claim 1, wherein the one or morehardware processors are further configured to frequency transform thereceived modulated physiological signal and the received modulatedplethysmographic waveform.
 4. The physiological monitoring system ofclaim 3, wherein the one or more hardware processors are furtherconfigured to cut off unwanted frequencies from the frequencytransformed physiological signal and the frequency transformedplethysmographic waveform.